Process for the manufacture of fuel briquettes



United States Patent- O PROCESS FOR THE MANUFACTURE OF FUEL BRIQUETTES Heinrich Dohmen, Deventer, Netherlands, assignor to N. V. Briko, The Hague, Netherlands, a Dutch limitedliability company No Drawing. Application May 7, 1956 Serial No. 582,928

Claims priority, application Netherlands May 12, 1955 19 Claims. (CI. 4415) The disadvantages adhering to the use of pitch as a binding agent for briquettes are known. Notwithstanding these disadvantages, pitch continues to be used as a binding agent for briquettes. The reason is that no suitable substitute for the pitch has heretofore been found.

The present invention now relates to a process in which briquettes are manufactured without'the use of pitch. The invention also relates to briquettes manufactured in accordance with the process.

According to the invention fuel briquettes are manufactured by treating lignite (brown coal) at an increased temperature with a small amount of an organic acid, particularly a lower carboxylic acid, mixing the product obtained, if desired, with another solid fuel than lignite in divided form, and pressing this mixture, or the abovedescribed product alone, to a briquette at an increased temperature.

The lignite coming from the-mine in a water-containing, mostly coarsely granular condition, before the treatment with the acid is preferably ground and made to granules, the greater part of which has a size of from approximately 0.5 to 1 mm., granules of larger and smaller dimensions also occurring. Granules up to a size of 3 mm. may be present between the finer granules without any objection and there is no lower limit to the size of the granules.

The lignite with the acid is brought to an elevated temperature, the minimum temperature being approximately 70 C. in practice. Results are also obtained at somewhat lower temperatures, e. g. 55 C., but the treatment with the acid then has to be continued unnecessarily long.

Temperatures higher than 70 C. are preferred, namely temperatures between 100 and 120 C., whilst an upper limit to the temperature is determined by the property of the lignite to bake together and carbonize.

By the treatment of the lignite with the organic acid the lignite is liberated from a part of the water present therein. Therewith modifications in the structure of the lignite take place which probably are of a colloid chemical character and an amount of water is driven out which is given off to the atmosphere. The formed mass is excellently suitable as a binding agent for briquctting coal, particularly pit coal, to fuel briquettes.

It has been found that acetic acid is excellently suitable for the treatment of the lignite; the water driven from the lignite is evaporated in the form of a dilute mixture of acetic acid in water. The acetic acid preferably is used in concentrated aqueous solution with approximately 80% acetic acid in an amount of cc. per kilogram of lignite.

The product obtained by the treatment of the lignite with the acid can as such be pressed to a briquette at an elevated temperature. Thereby a briquette is obtained which lies well on the fire and is weather and water-resistant.

This briquette can be pressed at a much lower pressure than is necessary for pressing lignite briquettes in the known manner. The use of pressures normally employed in the pressing of coal briquettes is, however, fully admissible.

Preferably the lignite treated with the organic acid is used as a binding agent for briquetting other fuels than the lignite itself, namely particularly for briquetting pit coal. Pit coal dust, culm and mud are available in large amounts and these forms of finely divided coal can be pressed to briquettes with an excellent result with the aid of the lignite treated with an organic acid.

Certain demands are made on the pit coal briquettes made up till now, but these demands all are equalled, and in most cases surpassed, by the briquettes manufactured in accordance with the present process with a weight proportion of parts of pit coal to 10 parts of the acid treated lignite. They lie well on the fire, are weather and water resistant and give better satisfaction than the known briquettes in respect of pressure resistance. Moreover, they do not give soot in the fire by which they are favorably distinguished from the known pitch briquettes, and the manufacture is not dangerous to health.

The above-mentioned proportion of 90 parts by weight of pit coal to 10 parts by weight of treated lignite is preferred, but also a smaller amount of lignite sufiices. The solidity decreases gradually with the amount of treated lignite and in general it is not recommended to use less than approximately 3% of the treated lignite. A sharp minimum limit cannot be given, however, and the properties not only depend on the amount of treated lignite, but also on the kind of pit coal used, the particle size, etc. There is no upper limit.

Before the treatment with the organic acid an amount of a carbohydrate or a carbohydrate ether can be added to the lignite and after thorough mixing of these starting materials the treatment with the organic acid can be carried out. Examples of carbohydrates suitable for this purpose are: potato-starch, sago, dextrin, corn meal and soybean meal and the carbohydrate can be added to the lignite in any proportion, a proportion between parts by weight and 10 parts by weight of lignite per part by weight of carbohydrate being preferred, however. Any other kind of starch in any proportion to the lignite can be used. An example of a suitable carbohydrate ether is Tylose (a brand name for cellulose ethers, such as, for example, methyl-cellulose and carboxy-methyl-cellulose).

The carbohydrate ethers usually are used in a proportion by weight of at most 5% of the amount by weight of lignite.

It is recommendable to add a small amount of solid or liquid paraffin wax to the lignite, the former for instance in molten condition and that, preferably, after the treatment of the lignite with the organic acid. Thereby the water-repellent capacity of the treated lignite is still increased.

It has appeared that coal having no or a slight baking capacity, produces briquettes which in the fire have a tendency to disintegrate. Surprisingly it now has been found that this drawback can be met by adding a slight amount of molasses to the lignite. Moreover, it has appeared, however, that by this addition also the binding capacity of the briquette is increased, i. e. the briquette hardens more quickly.

For this latter reason the recommendation to add molasses, consequently, does not especially relate to the manufacture of briquettes from coal without or with a slight baking capacity, but it extends to all kinds of coal.

The molasses can easily be mixed with the acetic acid used and can be mixed therewith before the addition of the acetic acid to the lignite, and that preferably in amounts of 30 to 40 g. per kilogram of lignite.

The invention is further elucidated by the following non-limiting examples.

3 Example 100 kilograms of lignite were ground and comminuted 'until the particle size of the greater part of the lignite was between 0.5 and 1 mm. and were heated at 110 to 115 C., 1500 cc. of 80% acetic acid being gradually added during heating, starting at a temperature of 75 C. The addition was carried out by spraying the acetic acid over the heated lignite as fine drops, the lignite being stirred. The color became darker.

Water escaped which was taken up by the atmosphere. After the acetic acid had been added, heating was continued for another short time, during which time 2500 g. of solid paraflin wax (melting point 68-70 C.) were added in molten condition and mixed.

The lignite product prepared in the above-described manner was gradually mixed with 900 kilograms of pit coal (ess-fine), the moisture content of which had been brought to approximately 1.8% by heating. Immediately after mixing the pit coal was heated with the aid of open steam of 140 C., the temperature of the coal increasing to 8590 C.

The mixture was supplied to the briquetting press, in which it was pressed to briquettes with a normal pressure. Already immediately after leaving the press the briquettes could be dropped on to a stone floor from a height of one half meter without breaking; after half an hour the admissible falling height was already a few meters and the weather resistance was sufiicient. The briquettes lay well in the fire and gave a fierce glow; they withstood poking.

If the lignite had not been treated with an organic acid, the briquettes coming from the briquetting machine disintegrated without more; they had neither a mechanical strength, nor a resistance to weather and water.

Example 2 92.5 kg. of lignite were ground and comminuted until the predominant particle size was between 0.5 and 1. mm. This material was intimately mixed with 5.0 kg. of potato-starch and 2.5 kg. of molten paratfin wax, whereupon the mixture was heated at 55 C. and 1 kg. of 80% acetic acid was added dropwise in the course of 20 minutes.

This binding agent (100 kg.) was mixed with 1000 gave a violent glow. With a small supply of air they can smoulder for several hours without disintegrating or extinguishing. They are weather and water resistant.

Instead of the ten-fold amount also a 14- to 15-fold amount of anthracite-fine can be pressed to briquettes with the aid of the binding agent of the present invention. The mechanical strength of the briquettes thus manufactured is then even somewhat higher than in the former case.

When the potato-starch was replaced by an equal amount of sago a binding agent was obtained which is suitable to be used for the briquetting of a 16-fold amount of pit coal (anthracite-fine). The mechanical strength is then somewhat less than in the above-described cases, but still amply sufficient for practical use.

Instead of anthracite-fine any other kind of pit coal in finely divided form can be briquetted with the aid of the binding agent prepared in accordance with the invention. The demands made on a briquetting binding agent for anthracite, however, are higher than those on a binding agent for pit coal with rest bakingcapacity.

The parafiin wax in the first place increases the water and weather resistance and in a less degree contributes to the mechanical properties which are the result of the capacity of the lignite, the carbohydrate, respectively to function in the converted form as a binding agent.

Example 3 s kilograms of lignite were ground to the same particle size as in Example 1 and thereupon were heated at C., a mixture of 1500 cc. of 80% acetic acid and 3.5 kilograms of molasses being sprayed over the lignite, starting at a temperature of 70 C., while stirring the lignite. The lignite became gradually dark brown, and water was given olf to the atmosphere. After the addition of the above-described mixture heating was continued for a further short time, 2 kilograms of liquid wax being gradually mixed with the mixture. The addition of the paraflin wax can also take place simultaneously with the addition of the mixture of acetic acid and molasses.

The binding agent thus prepared was gradually added to 900 kilograms of pit coal (meagre-fine) with a moisture content of 1.5%. Immediately before the addition of the binding agent the pit coal was heated for a short time with open steam of C. and was thoroughly mixed with the binding agent.

Thereupon the mixture was briquetted at a normal pressure.

The briquettes were immediately hard and lay well in the fire. They satisfied all requirements made on the pitch briquettes, but did not give of]? soot. If the binding agent was prepared in the same way, but without the addition of molasses, approximately 30% of the briquettes broke in the fire when it was poked; it also took a longer time before the briquette had obtained its max-- imum hardness.

What is claimed is:

1. A process for the manufacture of fuel briquettes which comprises mixing comminuted lignite with a watersoluble lower aliphatic monocarboxylic acid at a temperature between about 55 C. and carbonization temperature of the mixture, whereby a considerable part of the water contained in the lignite is expelled in admirture with said acid, and enhanced binding properties are imparted to the resulting product, and thereafter press ing the resulting product into briquette form at elevated temperature.

2. A process according to claim 1, wherein the lignite is preliminarily admixed with a carbohydrate in an amount not exceeding about 10% by weight of the latter, and the resultant mixture then subjected to treatment with the acid.

3. A process according to claim 1, wherein the lignite is preliminarily admixed with a carbohydrate ether in an amount up to about 5% by weight of the' latter, and the resultant mixture then subjected to treatment with the acid.

4. A process according to claim 2, bohydrate is starch.

5. A process according to claim 2, bohydrate is potato-starch.

6. A process according to claim 2, bohydrate is sago.

7. A process according to claim 3, bohydrate ether is methyl cellulose.

8. A process for the manufacture of fuel briquettes which comprises mixing comminuted lignite with acetic acid at a temperature between about 55 C. and car-v bonization temperature of the mixture, whereby a considerable part of the water contained in the lignite is expelled in admixture with acetic acid, and enhanced binding properties are imparted to the resulting product, and thereafter pressing the resulting product into briquette form at elevated temperature.

wherein the carwherein the carwherein the carwherein the car- 9. A process according to claim 8, wherein the acetic acid is in the form of a concentrated aqueous solution.

10. A process according to claim 8, wherein the acetic acid is present in the form of 15 cc. of 80% acetic acid per kilogram of lignite.

11. A process according to claim 8, wherein the comminuted lignite predominantly has a particle size of 0.5 mm.

12. A process according to claim 8, wherein the mixture of lignite and acid is heated to a temperature above 70 C.

13. A process according to claim 8, wherein about 30 grams of molasses are added per kilogram of lignite being treated with said acid.

14. A process according to claim 8, wherein paraiiin wax is added at a stage prior to the pressing into briquette form.

15. A process according to claim 13, wherein the molasses is mixed with the acid before the latter is added to the lignite.

16. A process for the manufacture of fuel briquettes which comprises mixing comminuted lignite with acetic acid at a temperature between about 55 C. and carbonization temperature of the mixture, whereby a considerable part of the water contained in the lignite is expelled in admixture with said acid, and enhanced binding properties are imparted to the resulting product, and thereafter mixing the latter with another comminuted solid fuel and pressing the mixture to briquette form at ele vated temperature.

17. A process according to claim 16, wherein said other fuel is coal dust. I

18. A process according to claim 16, wherein the other solid fuel is pit coal, and wherein the mixture pressed into briquette form contains 10 parts by weight of the treated lignite and 90 parts by weight of pit coal.

19. A process for the manufacture of fuel briquettes, which comprises admixing about 925 parts by weight of lignite with about parts by Weight of potato-starch, adding about 10 cubic centimeters of acetic acid, heating the mixture to about 80 C., adding about 25 parts by weight of molten parafiin wax to the resultant product, thereby producing a product which is useful as a binding agent, admixing about 1000 parts by weight of said binding agent with about 9000 parts by weight of coal dust, and pressing the mixture into the form of briquettes at about C.

References Cited in the file of this patent UNITED STATES PATENTS 719,830 Meade Feb. 3, 1903 1,607,012 McCrea Nov. 16, 1926 2,017,402 Komarek Oct. 15, 1935 FOREIGN PATENTS 437,870 Great Britain Nov. 6, 1935 

1. A PROCESS FOR THE MANUFACTURE OF FUEL BRIQUETTES WHICH COMPRISES MIXING COMMUNIUTED LIGNITE WITH A WATERSOLUBLE LOWER ALIPHATIC MONOCARBOXYLIC ACID AT A TEMPERATURE BETWEEN ABOUT 55*C. AND CARBONIZATION TEMPERATURE OF THE MIXTURE, WHEREBY A CONSIDERABLE PART OF THE WATER CONTAINED IN THE LIGNITE IS EXPELLED IN ADMIXTURE WITH SAID ACID, AND ENHANCED BINDING PROPERTIES, ARE IMPARTED TO THE RESULTING PRODUCT, AND THEREAFTER PRESSING THE RESULTING PRODUCT INTO BRIQUETTE FORM AT ELEVATED TEMEPRATURE. 